Current methods for measuring frequency modulation rate characteristics for a swept frequency signal (characterizing the swept frequency signal) use analog frequency demodulation such as, for example, frequency discrimination. However, bandwidth, linearity and accuracy when using analog frequency demodulation are limited. Additionally, analog frequency demodulation arrangements are difficult to calibrate and to maintain. They are also bulky, cumbersome and functionally inflexible.
Recently, characterizing swept frequency signals using high speed digital counting has been considered. However, digital counting requires sophisticated zero crossing (level crossing) timing measurements. This results in bulky, cumbersome and expansive apparatus which is not feasible for many portable applications, such as instrument-on-a-card (IAC) applications. In addition, digital counting is not adequate nor reliable when the received signal is noisy.
The present invention overcomes the aforenoted disadvantages.